EXCHANGE 


A  Comparative  Study  of  the  Slow  Combustion  of 

Methane  and  Methods  for  the  Determination 

of  its  Combustion  Products 


DISSERTATION 

Presented  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of  Doctor  of  Philosophy  in  the  Graduate 

School  of  the  Ohio  State  University 


BY 

FRANK  CARL  VILBRANDT,  B.A.,  M.  A. 


The  Ohio  State  University 

192O 


A  Comparative  Study  of  the  Slow  Combustion  of 

Methane  and  Methods  for  the  Determination 

of  its  Combustion  Products 


DISSERTATION 

Presented  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of  Doctor  of  Philosophy  in  the  Graduate 

School  of  the  Ohio  State  University 


BY 


FRANK  CARL  VILBRANDT,  B.A.,  M.A. 
\\ 


The  Ohio  State  University 
1920 


The  slov;  combustion  methods  consist  in  passing  the 
combustible  gas  slowly  into  an  oxidation  chamber  filled 
with  oxygen  or  air,  the  combustion  initiated  by  an  elec- 
trically heated  coil.  The  combustion  pipet  of  Clemens 
Winkler  {Ztsch.  anal*  Ghem.  28,  288 a  1889)  was  modified 
by  the  following  investigators":  Dennis  and  Hopkins 
(Dennis1  Gas  Analysis1  1913,  148),  Bretschger  (Treadwell- 
Hall.   'Quantitative  Analysis',  3rd  Edit.  J.  Wiley  &  Sons, 
p.  790),  Burrell  and  Siebert  (Bur.  Mines  Bull.  42,  17, 
1913),  Voldere  (Chem.  Ztg.  31,  1296,  1907),  Scott  (Ind. 
Eng.  Chem.  ].,  118,  1909),  Burrell  (U.S.  Pat.  1,  176,  199, 
L1917J),  Anderson  (Ind.  Eng.  Chem.  11,  292,  1919)  and 
Demorest  (Private  communication).   The  main  disadvantages 
of  this  method  are  the  incompleteness  of  combustion,  for- 
mation of  oxides  of  nitrogen,  breakage  of  apparatus  in 
the  hands  of  non-experts  and  errors  due  to  oxidation  of 
the  confining  material. 

The  capillary  method  of  combustion,  introduced  by 
Coquillon  (Compt.  rend*  85,  1106,  1877)  consisted  in  pass- 
ing a  previously  mixed  quantity  of  the  gas  and  oxygen  or 
air  through  a  heated  platinum  tube,  oxidation  produced 
only  in  the  presence  of  the  platinum.  'This  apparatus  was 
later  modified  by  Drehschmidt  (Ber.  21,  3242,  1888),  Wohl 
(Ber.  57,  433,  1904),  and  Roe hart  (Ztsch.  anorg.  Chem.  38, 
78,  1908);  The  same  method  modified  by  using  quartzware 
instead  of  platinum  for  the  capillary,  but  using  various 
forms  of  platinum  in  the  tube  for  catalysis  were  intro- 
duced by  Sabatier  ( *Die  Katalyse1  1st  edit.  Leipsig, 
p.  23),  Wilson  and  Mason  ^Proc.  Chem.  Soc.  [London 3  21, 
1296,  1905)  and  Mathers  and  Lee  (Chem.  Eng.  17.*  159,  1913). 
The  disadvantages  in  this  method  such  as  leakage  of  gas 
through  hot  platinum  and  the  high  cost  of  platinum  have 
been  fairly  well  taken  care  of  in  the  quartz  tubes. 

Each  modification  introduced  was  designed  to  over- 
come some  inherent  error  of  manipulation  or  apparatus. ' 
The  explosion  method  is  essentially  an  expert^s  method,, 
not  capable  of  giving  good  results  in  other  hands;  the 
capillary  method  requires  something  better  than  the  easily 
deterioratable  quartz,  and  the  slov/  combustion  method  re- 
quires the  elimination  of  breakage  due  to  local  heating  of 
the  capillary  and  oxidation  chamber  joint,  proper  manipu- 
lation or  apparatus  design  to  insure  completeness  of  com- 
bustion and  the  reduction  of  error  by  the  use  of  larger 
quantities  of  gas  for  the  combustion. 


The  investigation  carried  out  primarily  studied  the 
slow  combustion  method  with  the  view  of  eliminating  the 
above  undesirable  features  and  to  study  the  influence  of 
the  oxidation  effects  of  nitrogen  on  the  analyses  when  air 
was  introduced,  and  to  study  the  effects  of  the  products 
of  incomplete  combustion  of  the  methane. 

EXPERIMENTAL 

A  modified  Burrell  common  train  Orsat  laboratory  set- 
up, with  a  Kempel  temperature  and  pressure  compensator  was 
used.  The  absorption  reagents  used  were  potassium  hydrox- 
ide, alkaline  pyrogallates  and  acid  cuprous  chloride,  pre- 
pared according  to  Dennis  ( TGas  Analysis1,  1913,  pp.  160, 
225,  232,  233).   The  methane  used  was  prepared  by  the 
Glad  stone -Tribe  method  (J.  Chem.  Soc.,  [.London!  25,  684, 
1873;  45,  154,  1883)  from  methyl  iodide  and  Zn-Cu  couple, 
but  pure  methane  could  not  be  mad.e  by  this  method.   Other 
methods  yielded  no  better  results.   Methane  analysing 
84. 55/£  methane  12. 10/£  nitrogen  and  3.35?o  oxygen  by  the 
Dennis-Winkle r  method  was  used  for  the  investigation. 

STANDARDIZATION  OF  THE  TEMPERATURE  OF  THE  HEATED 
COIL.  The  references  in  the  literature  to  red  heat, 
cherry  red,  bright  red,  white  heat  and  dull  red  for  the 
temperature  of  the  electrically  heated  coil  was  too  inde- 
finite. Following  the  suggestion  of  Burrell  and  Siebert 
(idid.  p.  19)  who  measured  the  current  flowing  through  a 
platinum  coil,  but  gave  no  coil  dimensions  for  reproduc- 
tion of  their  temperatures,  in  this  investigation,  the 
temperatures  were  recorded  as  the  amperes  flowing  through 
a  #24  B,  &  S.  gage,  platinum  wire,  with  a  five  millimeter 
diameter  coil  of  four  turns  two  millimeters  apart. 

MODIFIED  ELECTRODES.   Difficulties  due  to  the  use  of 
electrodes  proposed  by  Bretschger  (loc.  cit.),  Dennis  and 
Hopkins  (loc.  cit.)  and  Porter  and  Ovitz  (Bur.  Mines  Bull. 
If  24,  1910)  by  breakage,  leaks  and  oxidation  of  the  mer- 
cury in  the  seal,  led  to  the  design  of  a  new  electrode 
consisting  of  sealed  in  platinum  coil  making  contact  with 
the  current  supply  by  means  of  mercury,  held  in  the  elec- 
trode tubes  by  rubber  tube  joint,  with  a  large  copper  rod 
to  which  the  supply  wires  were  connected.  (Seet^)  Figure 
1.) 


SLOW  COMBUSTION  PIPETS  AND  METHODS  OF  ANALYSIS. 

In  order  to  make  a  thorough  survey  of  the  difficul- 
ties inherent  in  each  of  the  more  modern  pipe ts  in  com- 
parison with  a  new  proposed  pipet,  the  following  pipets 
and  methods  were  studied:  Dennis  (ibid.  p.  149)  and 
Burrell  and  Siebert  (ibid.  p.  79).   These  were  modified 
to  make  the  Burrell  and  Siebert  either  water  cooled  or  air 
cooled  by  providing  an  air  jet  to  play  against  the  pipet 
and  also  a  continuously  flowing  film  of  water  over  the 
same.   In  addition  the  two  types  of  pipets  were  supplied 
with  the  new  central  burner. 

CENTRAL  BURNER  PIPET.   The  central  burner  pipet 
(Figure  1.)  is  provided  with  two  capillary  stop-cocks, 
B  and  C.   Manipulation  of  the  apparatus  is  carried  out  as 
follows:   With  C  closed,  air  or  oxygen  is  drawn  into  the 
pipet  by  lowering  the  mercury  leveling  bulb  attached  to 
the  pipet  at  F.  With  ten  cubic  centimeters  of  the  air  or 
oxygen  the  mercury  in  the  burner  tube  K  is  forced  out  by 
closing  B  and  opening  C.   Connections  are  made  with  the 
supply  of  gas  to  be  analysed;  with  the  temperature  of  the 
coil  attained  by  passing  a  measured  current  through  the 
coil,  the  gas  is  slowly  drawn  into  the  combustion  pipet 
by  opening  the  stop-cock  on  the  lowered  level  bulb;  the 
gas  on  entering  burns   with  a  small  flame  at  the  mouth 
of  the  quartz  burner  tube  K.  When  the  gas  has  all  been 
passed  into  the  chamber,  by  manipulation  of  the  cocks  and 
level  bulbs,  about  twenty  cubic  centimeters  of  the  gas  is 
withdrawn  and  passed  back  and  forth  into  the  apparatus 
several  times  to  insure  complete  combustion  of  all  the  gas 
which  would  normally  be  retained  in  the  capillary  connec- 
tions. .This  type  was  also  supplied  with  water  and  air 
cooling.   These  pipets  were  constructed  of  transparent 
quartz  to  enable  the  study  of  cooling  with  water  and  air, 
not  possible  with  glass  apparatus,  and  to  eliminate  the 
frequent  interruptions  necessary  to  replace  the  easily 
broken  glassware. 

The  capillary  quartz  tubes  were  of  special  construc- 
tion, with  enlarged  ends  to  enable  fitting  on  tubing; 
several  different  sizes  were  studied. 

The  effect  of  design  of  apparatus,  reduction  of  ap- 
paratus temperature  with  water  and  air,  effect  of  cutting 
off  the  current  after  the  initiation  of  the  combustion, 
the  effect  of  varying  the  temperature  of  the  platinum 


Figure   I.  Central  Upright  Burner  Pipette 


wire,  the  effect  of  varying  the  oxygen  to  gas  ratio,  the 
effect  of  rate  of  oxidation  and  presence  of  nitrogen  were 
studied  with  the  above  equipment. 

CALCULATIONS.   The  results  obtained  in  the  above 
study,  were  calculated  by  the  use  of  the  formulae  of 
Voldere  and  De  Smet  (Ztsch.  anal.  Chem.  49,  661,  1910), 
Anderson  (ibid.  p.  302)  and  by  the  author.   Using  the 
general  formula  for  the  complete  combustion  of  the  hydro- 
carbons of  the  methane  series: 


°2  =  nG02  *  (n+1)  H2° 
2 

Since  the  total  contraction  is  equal  to  the  sum  of  the 
volume  of  the  hydrocarbon  and  of  the  oxygen  required  minus 
the  carbon  dioxide  formed,  or 

T.C.  equals  V  plus  Qg  minus  COg 

then         Og  required  equals   3n  plus  1. 

2 

COg  equals  nV 

T.C.    "   5  plus  n  . 


Since  the  gases  deviate  from  the  gas  laws  according  to 
Wohl  (Ber.  37_,  429,  1904),  Raleigh,  Leduc,  Baume,  Perrot 
(J.  Chem.  Phys.  7,  367,  1909)  and  Dennis  (ibid.  p.  139) 
it  was  necessary  to  make  corrections  for  these  deviations. 
The  equations  for  the  reaction  of  methane  and  hydrogen 
with  oxygen  then  becomes; 

0.999  CH4  plus  2.000   Og  equals  0.954  COg  plus  2  HgO 
2.004  Hg    "   1.000   Og    "     2  HgO 
or,     COg  equals  0.995  CH4 

T.C.   ts     1.499  Hg  plus  2.007  CH4 

In  order  to  eliminate  repeated  development  of  correct 
equations  on  the  basis  of  carbon  dioxide  remaining  in  the 
gas  after  combustion  a  correction  factor  was  developed 
for  the  different  hydrocarbon  values  following  the  plan 
of  Anderson  (ibid.  p.  302) 


6 

SUMMARY  OF  COMBUSTION  DATA.   The  data  obtained  in 
this  investigation  is  compiled,  in  Table  1,  the  results 
being  averages  of  from  three  to  six  determinations,  includ- 
ing all  data  such  as  type  of  apparatus,  modification, 
color  of  heating  coil,  current  flowing  through  wire,  rate 
of  gas  flow,  ratio  of  oxygen  to  gas  sample,  analyses  and 
estimated  average  completeness  of  combustion. 

DISCUSSION  OF  RESULTS. 

FORMATION  OF  OXIDES  OF  MERCURY.   Many  determinations 
not  recorded  in  Table  1  were  eliminated  because  of  forma- 
tion of  oxides  of  mercury  due  to  the  high  local  heating 
of  parts  of  the  apparatus  in  contact  with  the  mercury  con- 
taining fluid.   Mercury  oxidation  dees  not  affect  methane 
percentages  but,  by  increasing  the  total  contraction,  in- 
creases the  hydrogen  percentages.   Two  forms  of  the  ox- 
ides of  mercury  were  found  in  the  pipets  during  some  of 
the  worthless  combustions;-  red  and  brownish  yellow.  The 
red  variety  occurred  at  high  coil  temperatures  and  the 
yellow  at  low  heats. 

INFLUENCE  OF  WIRE  COIL  TEMPERATURE.   The  results 
show  incompleteness  of  combustion  with  the  coil  heated 
with  below  6*8  amperes;  additional  experimentation  showed 
that  no  ignition  of  the  gases  resulted  when  less  than 
3.5  ampere  were  used  to  heat  the  coil,  consisting  of  four 
turns  of  #24  gage  platinum  wire,  2  millimeters  between 
coils  and  5  millimeter  coil  diameter.   After  initial  ig- 
nition of  the  gas  the  temperature  of  the  coil  had  no 
effect. 

INFLUENCE  OF  RATE  OF  COMBUSTION.   After  visible  com- 
bustion has  once  been  started  the  rate  of  gas  flow  up  to 
25  cubic  centimeters  per  minute  has  no  effect  on  the 
analyses,  except  that  precautions  must  be  taken  where 
mixtures  approximating  explosive  proportions  are  used  that 
destructive  explosions  do  not  occur. 

INFLUENCE  OF  RATIO  OF  OXYGEN  TO  COlViBUSTIBLE  GAS. 
With  ratios  approximating  2.0  oxygen  to  1.0  gas,  or  no 
excess  oxygen,  results  are  erratic.   With  25%  excess 
oxygen,  or  with  ratios  of  2.5  to  1.0  uniform  and  agree- 
ing results  were  obtainable .  Nothing  is  gained  by  in- 
creasing the  oxygen  ratio  above  this  value. 


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i, 

j 
fr 

t 

1 

L 

o 

ro 

p 

s 

& 

i 

P 

H 

c 

o1 

CXI 

O 

*>  d- 

f  P 

3 
^     ? 

2 

w 

H- 

d- 
-o 

9 

Series   Wo. 

IIos.   of  runs. 

Type  of  Ap- 
paratus 

Modifica- 

i    • 

Color  of                g 
Wire 

Amperes  flow- 
ing through          ^ 
coil                   0 
o 

,_, 

^ 

^ 

!-> 

^_, 

_ 

ro 

ro 

ro 

Rate  of  gas  f£bw  § 

GO 

= 

co 

0 

CO 

0 

0 

ro 

o 

0 

cn 

0 

cc/min.               §3 

f 

cx) 

cxi 

ro 

CX) 

ro 

ro 

ro 

ro 

03 

ro 

ro 

ro 

*   ^ 

Ratio   of 

Pd 

O 

O 

ro 

o 

cn 

cn 

cn 

cn 

O 

cn 

ro 

^ 

Oxygen/Methane  I 

M 

CO 

CO 

co 

CO 

CO 

co 

CO 

CO 

co 

CO 

CO 

CO 

^ 

^v 

cn 

lf^ 

cn 

£•>• 

ir» 

h^> 

£=• 

tf* 

lf« 

rt^ 

H^ 

Cn"2n  2                  tr1 

O 

co 

cn 

ro 

cn 

*> 

cn 

cn 

CD 

lp» 

cn 

cn 

cn 

of 

^ 

ro 

IP1 

O'J 

H 

0 

CO 

ro 

t-< 

o 

%                                               (r) 

CO 

~ 

CO 

CO 

CO 
CX) 

co 
ex) 

co 

CX) 

CO 
Cxi 

co 

CXI 

CO 
CX) 

CD 

CO 

CO 

CO 

Methane 

W 

co 

JL 

Oi 

to 

CO 

CO 

co 

CO 

O 

Q 

<j 

^3 

<rt 

° 

CD 

CD 

CO 

cr> 

ro 

"^ 

-a 

cn 

* 

*• 

H-1 

o 

O 

o 

M 

a 

o 

O 

o 

O 

O 

o 

O 

Hydrogen 

to 

l_i 

cn 

cn 

cn 

-0 

CD 

CD 

rf^ 

^ 

-o 

-0 

d 

co 

CX) 

-o 

*• 

CO 

h^ 

*^ 

CO 

CXJ 

co 

-0 

to 

/° 

M 

M 

\-> 

\-> 

K-1 

w 

,_, 

M 

M 

M 

t-" 

H 

Residual  Gas 

o 

ro 

cn 

rf* 

cn 

cn 

cn 

cn 

cn 

cn 

cn 

cn 

Co 

O 

_j 

CD 

cn 

CXI 

Jk 

r^ 

<j 

d9* 

rf^ 

cn 

J* 

O) 

O> 

co 

en 

vp> 

to 

6 

Oi 

Co 

to 

0 

H-1 

8 

e 

0 

o 

ft 

CO 
to 

to 

CO 

to 

to 

to 

CO 

to 

CO 

to 

O 

CO 

to 

CO 

CO 

O 

CO 
CO 

to 

CO 

Estimated  Av. 
Completeness  of 

cn 

ro 

Oi 

cn 
O 

s 

cn 

CO 

CD 

CD 

ro 

s 

<J 

CO 

ro 

CO 

£ 

Combustion 

Remarks 


10 


1 

t-1 
exi 

ro 
i 

i 

Series   No. 

CT 

P 

p        PJ 

0           0*          P 

o 

& 

p 

exj 

V-1 

ro        to 

|N>                  \->                 \-> 

CXI 

ro 

ro 

Nos.   of  runs- 

„ 

_ 

_ 

TJ 

""" 

H- 

M 

Type  of  Ap- 

"- 

T^r 

** 

P 

paratus 

- 

H-    O 

o 

^ 

HJ        H' 

H- 

^^* 

O    M 

M 

• 

2 

—              —               z 

3 

s 

H- 

1      — 

H-    O 

H- 

3 

CD 

01     <+ 

H-  cn 

w 

H« 

H- 

Modifica- 

:   - 

CD'  ^ 

CD 

M 

tion 

fT^ 

*••••• 

•• 

•* 

H- 

,v__x 

0- 

O 

^ 

Cd 

1 

=         =       H- 

H- 

Color  of  Wire       co 

pt- 

8 

— 

cn 

£• 

<D 

p* 

SL 

d- 

§, 

= 

= 

S            3 

Cfl 

S             =          P 

w 
r* 

S 

± 

Teclu 
Burner 

Amperes  flow-        » 
ing  through 
coll*                  ^3 

« 

o 

o 

w 

>* 

H-1 

—             -» 

CD       o       ro 

0 

^ 

H-» 
CD 

Rate  of  gas  flows 

r* 

cc/min«               co 

w 

i-3 

M 

ro 

ro 

CXI           ^ 

exi        ro        ro 

CXJ 

ro 

ro 

Ratio   of                 o 

M 

en 

ro 

en        O 

•  O        en        ro 

o 

en 

ro 

Oxygen/Methane    ^ 

^ 

0 

00 

oo 

CD           CD 

CO           CO           CD 

00 

CO 

-a 

A       TT                    O                                                       t~J 

0 

O 

*£»         »£• 

rf*       rf*       i—1 

en 

ro 

Cxi 

CO 

c*- 

^ 

^_, 

en       en 

exi       exj       H-1 

O 

CX! 

CO 

°? 

to 

ro 

CXJ          tO 

en       to       to 

O 

CO 

cxj 

/o                                           CO 

^ 

00 

CO 
O 

OP           O3 
Cxi        tT- 

CD            CO            CO 

exi       exj       i^ 

CD 
CX) 

CD 

I-1 

ro 

Methane 

en 

o 

-o        O 

CO          O          O 

CX) 

o 

en 

tf 

en 

o 

ro       ui 

to       ro       H* 

oo 

ro 

f-< 

0 

o 

0       0 

O         O         0 

M 

H 

H- 

Hydrogen 

ro 

H 

-si          O3 

ff>-          »^          M 

cn 

CXJ 

•£» 

o/ 

ro 

-o        ri^» 

-<l           -^0           00 

ro 

cn 

ro 

/° 

t—  ' 

i_i        t~j 

h-«           H1           f-* 

M 

H-J 

ro 

Residual  Gas 

en 

CO 

en       en 

en       en       Co 

en 

-a 

cn 

ro 

M 

oo 

CO 

rf^       tvi 

en       en       co 

jfs.           I—  <           H-  ' 

8 

en 
ro 

O 

f« 

to 

CO 

to       to 

CO          CO          CO 

to 

to 

CD 

Estimated  Av. 

CO 

CO         tO 

CO         co         -~4 

CO 

cn 

en 

Completeness  of 

CO 

to 

to 
-a 

CO         to 

en       en       exj 
to       exi       en 

8 

to 

O 
-a 

Combustion 

Remarks 


11 

INFLUENCE  OP  FORM  OR  TYPE  OF  P1PET.   Quart fcware  ap-   . 
paratus  gave  as  good  results  as  glass.   The  results  with 
the  new  Central  Burner  pipet,  which  does  away  with  the 
heating  of  the  capillary  and  pipet  joint,  and  uses  the 
principle  of  burning  the  gas  in  the  center  of  an  atmos- 
phere of  oxygen,  eliminating  the  flame  front  effect  of 
the  Winkle r  modified  pipets,  gave  results  more  uniform  and 
higher  than  with  other  pipets.   Under  varying  conditions 
this  form  of  pipet  averages  a  completeness  of  combustion 
of  99.85^  with  a  maximum  deviation  from  the  mean  of  0.86/o 
below  and  0.92/b  above  this  figure.   The  Winkle  r  modifica- 
tion pipet  averaged  0.21$  lower  completeness  of  combustion 
with  a  deviation  of  2.5%  above  and  5.43$  below.   The 
Burrell  pipet  averaged  0.53$  higher  with  a  lower  limit  of 
1.73/0  and  an  upper  limit  of  1.63$.   The  deviations  occur- 
ring in  pipets  other  than  the  Central  Burner  occurred  with 
variations  in  oxygen  gas  ratio,  indicating  a  larger  range 
with  the  new  pipet.   The  results  with  this  pipet  are  not 
affected  by  method  of  heating,  rate  of  cooling,  tempera- 
ture of  the  apparatus  and  rate  of  gas  flow  up  to  25  cubic  . 
centimeters  per  minute. 

FORMATION  OF  OXIDES  OF  NITROGEN.   Determination  of 
the  quantity  of  oxides  of  nitrogen  with  sulfanilic  acid 
and  a-naphthylamine  in  acetic  acid  solution  showed  in*- 
creasing  amounts " of  nitrites  in  the  alkali  with  increase 
in  oxygen  excess.   The  temperature  of  the  wire  had  no 
effect.   However,  the  maximum  quantity  found  was  only  0.05 
cc.,  the  limit  of  accuracy  in  reading  the  Hempel  gas 
buret.   This  agrees  v:ith  the  conclusions  of  Dennis  (ibid) 
and  Burrell  and  Siebert  (ibid).   The  formation  of  oxides 
of  nitrogen  in  larger  quantities  in  the  Dennis -Winkle r 
pipet  than  in  other  types  confirms ' the  conclusions  of 
White  (J.  Amer.  Chem.  Soc.  23,  476,  1901). 

FORMATION  OF  FORMIC  ACID  AND  FORMALDEHYDE.   Rerun 
determinations  as  done  in  the  oxides  of  nitrogen  study 
were  made  to  determine  the  amount  of  formic  acid  and  for- 
maldehyde formed  during  the  combustion.   The  rosaniline 
hydrochloride  test  of  Bone -Wheeler  (J.  Chem.  Soc.  London, 
85,  1083,  1902)  and  the  phloroglucinol  test  (Allen:  Com- 
mercial Organic  Analysis,  Vol.  VIII,  p.  171)  were  used 
for  formaldehyde  and  the  modified  Hauser  (Chem.  Ztg.  3£, 
57,  1915;  Allen's  Commercial  Organic  Analysis,  Vol.  VIII, 
p.  191)  test  was  used  for  the  detection  and  determination 
of  formic  acid.   Only  traces  of  formaldehyde  were  formed 
in  the  combustion  pipets.   Formic  acid  was  also  found, 
but  in  quantities  which  were  but  slightly  greater  than 


12 

the  error  in  reading  the  buret;  the  largest  volumes  found 
were  0.07  and  0.068  cc.  with'  one  set  of  runs  running 
0.143  cc.   The  results  show  larger  quantities  formed  when 
the  ratio  of  .oxygen  to  gas  is  low. 

CAPILLARY  COMBUSTION  DATA. 

The  quartz  capillary,  eliminating  the  presence  of  an 
oxidizable  confining  metal  mercury  and  giving  intimate 
contact  of  the  mixed  gases  with  the  catylist,  gave  an 
average  estimated  completeness  of  combustion  of  99.56/0 
with  a  maximum  deviation  from  this  mean  of  0.79%  above 
and  0.58%  below.   Increase  in  the  rate  of  gas  flow  over 
the  platinum  decreases  the  completeness  of  combustion. 
The  slower  the  rate  of  gas  flow  the  lesser  the  number  of 
repeated  passages  of  the  gas  over  the  platinum  to  bring 
about  complete  combustion,  determined  by  non-glowing  of 
platinum. 

DEVITRIFICATION  0?  QUARTZ  CAPILLARY  TUBES. 

Fused  transparent  quartzware  deteriorated  very 
rapidly  when  gases  were  burned  in  capillaries  made  of 
this  material.   The  devitrification  initiated  at  points 
of  contact  of  the  platinum  with  the  quartz,   With  the 
Teclu  burner,  only  seven  determinations  were  possible 
before  the  frosting  was  too  pronounced  to  use  the  capil- 
lary for  further  work.   With  the  blast  flame  directed 
against  the  outside  of  the  capillary  with  platinum  wire 
inside  for  the  catalyst,  one  tube  broke  after  the  fourth 
run5  the  second  tube  after  five  runs.   Using  in  addition 
to  the  above  a  platinum  foil  on  the  outside  of  the  tube 
to  protect  it  against  the  direct  blast,  nine  determina- 
tions were  accomplished  before  the  tube  broke.   With  the 
foil  inside,  seven  runs  was  the  maximum.   Microscopic 
examination  of  the  wires,  foils  and  quartz  tubing  showed 
a  deep  checking  on  the  quartz,  and  many  particles  of  the 
fused  quartz  impinged  on  the  wires  and  foils.   A  few 
crystals  of  quartz  were  also  isolated,  these  having  a 
greater  coefficient  of  expansion  than  the  fused  variety, 
probably  caused  the  splitting  off  of  the  latter  when  the 
tubes  were  subjected  to  changes  in  temperature.   Fused 
quartz  as  combustion  tubing  in  direct  contact  with 
platinum  as  a  catalyst  deteriorated  too  rapidly  in  this 
investigation  to  be  accepted  as  a  satisfactory  substi- 
tute for  Coquillon's  platinum  capillary. 


13 

CONCLUSIONS. 

The  investigation  presents  the  following  conclusions: 

1.  The  development  of  a  new  type  of  combustion  pipet, 
the  Central  Burner,  which  eliminates  inherent  errors  in 
the  construction  and  manipulation  of  other  combustion 
pipets:  results  with  this  pipet  are  not  appreciably  in- 
fluenced by  rate  of  combustion,  temperature  of  the  coil  or 
excess  oxygen; 

2.  A  satisfactory  gas  pipet  electrode  has  been  de- 
veloped, eliminating  troublesome  mercuric  oxide  forma- 
tion; 

3.  The  elimination  of  the  long  capillary  on  the  com- 
mon pipets  tends  toward  conservation  of  apparatus; 

4.  The  proper  excess  of  oxygen  for  combustion  with 
the  old  pipets  is  twenty-five  per  cent; 

5.  The  temperature  of  the  heating  element  can  be 
standardized  by  measuring  the  current; 

6.  The  effect  of  the  formation  of  oxides  of  nitro- 
gen on  the  analysis  is  negligible; 

7.  The  effect  of  the  formation 'of  formaldehyde  and 
formic  acid  on  the  analysis  is  negligible j 

8.  Fused  quartz  gives  more  satisfactory  service  than 
glass  as  a  material  of  construction  for  combustion  pipets; 

9.  Capillary  combustions  with  platinum  as  catalysts 
gives  very  good  results,  but  quartz  capillary  does  not 
stand  up  under  this  treatment. 


PAT.  JAN.  21.  1908 


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